Download Chap21 - Nicholls State University

Bacteria, Viruses and Protistans (chap 18)
1. Bacteria – Most ancient forms of life (Table 18.1)
1. Great metabolic diversity (Table 18.2)
1. Photoautotrophic – synthesize own organic compounds <<sugars>> using sunlight and carbon dioxide
2. Photoheterotrophic – use sunlight, but carbon comes from organic compounds
3. Chemoautotrophic – produce organic compounds using carbon dioxide and energy in inorganic substances
4. Chemoheterotrophic – cannot produce own organic compounds
1) Parasitic – draw nutrition from living hosts <<germs>>
2) Saprobic – obtain nutrition from products, wastes, or remains of other organisms
2. Bacterial sizes and shapes
1. Usually 1-10 micrometers
2. Three basic shapes
1) Coccus – spherical
2) Bacillus – rod-shaped
3) Spirillum – spiral-shaped
3. Structural features
1. Prokaryotic – no nucleus [or other membrane-bound organelles]
1) Metabolism occurs in cytoplasm or at plasma membrane
2) Proteins assembled on floating ribosomes
2. Nearly all possess cell wall
1) Gram-positive and gram-negative
3. Has jellylike capsule for attachment and to deter antibiotic activity
4. May have filamentous structures attached to cell wall
1) Flagellum – for movement
2) Pili – for attachment [incl. conjugation]
4. Bacterial reproduction
1. Binary fission – single “chromosome” (Fig. 18.5)
2. Plasmids carry only a few genes – replicated independently of main “chromosome”
5. Bacterial classification
1. Traditionally characterized by staining reactions, cell shape, metabolic patterns, and mode of nutrition
2. True classification based on evolutionary relationships becoming possible due to biochemistry studies
6. Major groups of bacteria
1. Archaebacteria
1) First living cells – exist in unusual habitats
2) Methanogens (“methane-makers”)
1) Inhabitat swamps, mud, sewage, and animal guts
2) Make ATP anaerobically by converting carbon dioxide and hydrogen to methane
3) Halophiles (“salt-lovers”)
1) Tolerate high salt environments [brackish ponds, salt lakes, volcanic vents, etc.]
2) Most are heterotrophic aerobes
4) Extreme thermophiles (“heat-lovers”)
1) Live in hot springs and volcanic vents
2) Use hydrogen sulfide for ATP formation
2. Eubacteria
1) Photoautotrophic eubacteria
1) Cyanobacteria [blue-green algae] are photosynthetic <<carbon dioxide and water>>
2) Green and purple bacteria use hydrogen sulfide and hydrogen gas for photosynthesis
2) Chemoautotrophic eubacteria
1) Most important are nitrifying bacteria – nitrogen cycle
2) Use ammonia in generating ATP
3) Chemoheterotrophic eubacteria
1) Some are major decomposers in soil
2) Actinomycetes produce antibiotics, Lactobacillus used in dairy product conversions, etc.
3) Some E. coli causes serious diarrhea, Clostridium botulinum – botulism, Borrelia burgdorferi – lyme
disease
2. Viruses
1. Defining characteristics
1. Noncellular infectious agent
1) Consists of nucleic acid core (DNA or RNA) surrounded by protein coat
2) “Reproduces” by causing host cell to make more viral particles
2. Vertebrate immune system can detect and fight viruses, but viruses continually mutate
2. Examples of viruses (Table 18.3)
1. Bacteriophages – infect bacterial cells
2. Animal [human] viruses – influenza, chickenpox, colds, HIV (AIDS)
3. Plant viruses – usually rely on insects to provide penetration of host cells
3. Infectious agents smaller than viruses
1. Prions – infectious protein particles (“Mad Cow” disease) that destroys nervous system
2. Viroids – naked pieces of RNA (no protein coat) that cause plant diseases
4. Viral multiplication cycles (Figs. 18.12 & 18.13)
1. Steps of viral replication
1) Virus “recognizes” and attaches to host cell
2) Nucleic acid core enters host cell
3) Viral genes direct host cell to replicate new viral components
4) Host cell ruptures releasing new viral particles
2. Replication can proceed by two pathways
1) Lytic pathway [see above] (Fig. 18.12)
2) Lysogenic pathway – latent period in host (Fig. 18.13)
3. Protistans – simplest eukaryotic organisms, unicellular and multicellular
1. Predatory and parasitic molds
1. Chytrids and water molds
1) Chytrids – decomposers or parasites in muddy or aquatic habitats
2) Water molds – attack weakened fish or land plants (e.g., Irish potato famine)
2. Slime molds (Fig. 18.15)
1) Heterotrophic, free-living, amoebalike protistans
2) Feeds by engulfing food particles; reproduces by spores
3) Two groups – cellular slime molds and plasmodial slime molds
2. Animal-like protistans – protozoans
1. Defining characteristics
1) All are predators or parasites
2) Mostly asexual reproduction by fission or budding
3) A few cause diseases in humans <<and other animals>>
2. Amoeboid protozoans (Fig. 18.17)
1) Pseudopodia – extensions of cell body
2) Amoeba proteus – lab animal; Entamoeba – causes dysentery
3) Foraminiferans – shelled forms; radiolarians – shells of silica; heliozoans – needle-like pseudopods
3. Ciliated protozoans
1) Numerous cilia – beat in synchrony
2) Paramecium – sexual reproduction involves conjugation (Fig. 18.18)
4. Flagellated protozoans (Fig. 18.19)
1) One or more whip-like entensions
2) Tichomonas vaginalis – spread by sexual contact; Giardia lamblia – mild diarrhea to death;
Trypanosoma – African sleeping sickness
5. Sporozoans (Fig. 18.20)
1) Parasitic – sporozoite stage usually transmitted by insects, and encysted stage
2) Plasmodium – malaria (transmitted by mosquitoes); toxoplasmosis – can cause birth defects
(transmitted from cats to humans through infected feces)
3. (Mostly) Single-celled photosynthetic protistans
1. Euglenoids
1) Mostly photosynthetic autotrophs, some are heterotrophic
2) Euglena – flexible pellicle, flagellum, eyespot
2. Chrysophytes
1) Golden-brown algae
2) Diatoms – shells of silica
1) Bottom of marine food chain
2) Commercially valuable as abrasives and filtering materials
3. Dinoflagellates
1) Two flagella located in grooves in cell wall
2) Some cause “red tides” (producing neutotoxins)
4. (Mostly) Multicelled photosynthetic protistans
1. Red algae (Fig. 18.23a)
1) Pigments trap sunlight in deep marine waters
2) Complex asexual and sexual life cycles
3) Some aid in reef building; others yield agar
2. Brown algae (Fig. 18.23b)
1) Includes kelps of intertidal zones
2) Plantlike – with leaflike blades on a stemlike stipe attached to a rootlike holdfast; some have floats
3) Produce algin – used as a thickening or suspension <<smoothing>> agent
3. Green algae (Fig. 18.24)
1) Grow nearly everywhere
2) Same pigments as land plants; store carbohydrates as starch
3) Some are symbionts with fungi <<lichens>> and other organisms, others are colonial (Volvox), many
live singly (Chlamydomonas)
Plants and Fungi (chap 19)
4. Evolutionary trends among plants
1. Overview of the Plant Kingdom
1. Mostly multicelled photosynthetic <<green>> autotrophs
2. Most have vascular tissues for transport of water and nutrients; and roots, stems, and leaves
3. Nonvascular plants [e.g., bryophytes] lack true roots or leaves
2. Evolution of roots, stems, and leaves
1. Roots – absorption of water and minerals
2. Shoots <<stems + leaves>> – exploiting sunlight and absorbing carbon dioxide
3. Lignin – hard substance in cell wall allowing extensive growth <<taller plants>>
4. Cuticle – covering stems and leaves to minimize water loss; evaporation <<transpiration>> controlled by
stomata
3. From haploid to diploid dominance (Fig. 19.2)
1. Simple aquatic plants <<algae>> dominated by haploid phase
2. Complex land plants dominated by diploid sporophyte
1) Parts of sporophyte undergo meiosis to produce haploid spores
2) Spore develops into gametophyte, which produces gametes <<eggs and sperms>>
4. Evolution of pollen and seeds
1. Spores of some algae and simple vascular plants are all alike [homosporous]
2. In gymnosperms and angiosperms <<flowering plants>>, spores are of two types [heterosporous]
1) Pollen grain = male gametophyte
2) Female gametophyte remains within plant, producing seeds
5. Bryophytes – mosses, liverworts, and hornworts [mosses are the most common] (Fig. 19.4)
1. Lack xylem and phloem <<water and nutrient conducting tubes>>; rhizoids attach gametophyte to soil
2. Gametophyte
1. Developments from spore – haploid, leafy, independent plant
2. Contains archegonium <<egg>> and antheridium <<sperms>>
3. Sporophyte
1. Developments from zygote [fertilized egg] – diploid and dependent on gametophyte
2. Composed of foot, stalk, and capsule [sporangium] that contains spores
6. Existing seedless vascular plants – sporophyte is dominant; xylem and phloem are present
1. Whisk ferns
1. “Twiggy” looking plant – no roots or leaves [photosynthesis occurs in stem tissue]
2. Underground rhizome; sporangia on branches
2. Lycophytes
1. Once tree-sized, but now small club mosses on forest floor
2. True roots, stems, and small leaves – cone-like strobili contain sporangia
3. Horsetails or scouring-rushes
1. Once treelike, now common “bamboo-like” roadside plants around here
2. Roots, rhizomes <<underground stems>>, aerial stems <<with silica>>, but no true leaves [stem is
photosynthetic]
4. Ferns
1. Roots, rhizomes, and big leaves [fronds – young ones called fiddleheads]
2. Sporangia are clustered into sori on the underneath of fronds
7. Gymnosperms – plants with “naked” seeds
1. Life cycle (Fig. 27.10)
1. Microspore (in “male” cone) develops into pollen grain – wind pollination
2. Megaspore develops into ovule [immature seed] – exposed or in “female” cone
2. Conifers
1. Cone-bearing trees with needlelike or scalelike leaves [mostly evergreen]
2. Male pollen cones and female seed cones
3. Fertilization results in a zygote that develops into an embryo within the seed
3. Lesser known gymnosperms
1. Cycads
1) Small palmlike trees – 100 species of the tropics and subtropics
2) Large pollen and seeds cones on separate plants
2. Ginkgos [or Maidenhair tree]
1) Only one species survived the Mesozoic – living fossil
2) Leaf fan-shaped, seed exposed
3. Gnetophytes [e.g., Mormon tea]
1) Found in tropical and desert areas
8. Angiosperms – flowering plants (Figs. 19.11 and 19.12)
1. Produce flowers with special tissues to protect ovules and seeds
1. Most species coevolved with pollinators
2. Dominated the land for 100 million years
2. Monocots and dicots
1. Monocots – grasses [inclu. cereal grains], lilies, etc. <<one cotyledon, flower parts in 3's, etc.>>
2. Dicots – trees [except conifers], shrubs, and herbaceous plants <<two cotyledons, flower parts in 4's or 5's,
etc.>>
3. Life cycle
1. The diploid sporophyte has roots and shoots, and retains and nourishes the gametophyte
2. Flowers attract animal <<mostly insect>> pollinators
1) Sepals and petals
2) Stamen – anther and filament
3) Pistil – stigma, style, and ovary [containing ovules]
3. Embryos nourished by endosperm within seeds, which are packaged inside fruits
9. Fungi
1. “Characteristics”
1. Three major groups [zygomycetes <<bread molds>>, sac fungi, and club fungi] and one “catch-all”
category [imperfect fungi]
2. Nutritional modes
1) Heterotrophs that utilize organic matter
1) Saprobes – get nutrients from nonliving matter [valuable decomposers]
2) Parasites – thrive on tissues in living host
2) Digest the surrounding food and absorbs nutrients
3. Life cycle
1) Reproduce both asexually and sexually, producing spores
2) Food-absorbing part is a mesh of branching filaments [the mycelium, composed of individual hyphae]
2. Classification of fungi
1. Zygomycetes (Fig. 19.15)
1) Mostly bread molds
2) Reproduces asexually by small, dustlike spores and sexually by zygospores
2. Sac fungi (Fig. 19.16)
1) Edible morels and truffles, plus Penicillium [antibiotics] and Aspergillus [soy sauce]; also single-celled
yeasts [bread and alcohol]
2) Larger ones produce structures with sacs that contain ascospores; yeasts mostly reproduce asexually, by
budding
a. Club fungi (Fig. 19.14)
3) Mushrooms, puffballs, shelf fungi, rusts, and smuts
4) Produce basidiospores on club-shaped cells; mushroom has stalk and cap [with gills]
4. Imperfect fungi
1) All fungi lacking a sexual stage – gets moved out when sexual spore are discovered
2. Symbiotic associations between fungi and plants
1. Lichens
1) Mutualistic associations between fungi and cyanobacteria or green algae
1) Algae is protected from drying out
2) Fungi feeds on sugars produced by the algae
2) Can live in inhospitable places such as bare rock and tree trunks, but are sensitive to air pollution
3) Three body forms – crustose, foliose, and fruticose
2. Mycorrhizae
1) Symbiotic relationship in which fungi hyphae surround roots of woody plants
2) Increases the absorption power of the roots [water and minerals]
Animals: The Invertebrates (chap 20)
1. General characteristics of animals
1. Multicellular, heterotrophic, aerobic, reproduce sexually, motile at some point in life cycle
2. Life cycles include period of embryonic development; germ tissue layers (ectoderm, mesoderm, endoderm)
give rise to adult organs
3. Diversity in body plans
1. Vertebrates – have a backbone; invertebrates – lack a backbone
2. Body symmetry
1) Radial – round
2) Bilateral – left and right sides
1) Show anterior (head), posterior (tail), dorsal (back), and ventral (belly) orientations
3. Cephalization – have a definite head, usually with feeding and sensory features
4. Type of gut
1) Saclike – with one opening
2) Complete – with two openings (mouth and anus)
5. Body cavities
1) Coelom – space between gut and body wall; lined with peritoneum
2) False coelom – such as in roundworms; not lined with peritoneum
3) No coelom – packed solidly with tissue
6. Segmentation – composed of repeating body units (may be grouped and modified for specialized tasks)
4. Possible origin of animals
1. Compartmentalization of a ciliate (like Paramecium)
2. Arose from colonial organisms like Volvox
2. Sponges – 8,000 species
1. Asymmetric body with no true tissues or organs
1. Flattened cells cover the exterior
2. Collar cells line interior chambers – move water and trap suspended food particles
3. Jelly-like matrix (with wandering amoeboid-like cells) between the two
2. Reproduce asexually (by fragmentation) and sexually (zygote produces swimming ciliated larva)
3. Cnidarians – tissues emerge (11,000 species)
1. Tentacled, radial animals
1. Inclu. jellyfishes, sea anemones, hydrozoans
2. Name comes from ability to sting by discharging nematocysts
2. Body plans
1. Medusa – jellyfish body plan; polyp – tubelike and usually attached (may be solitary or part of a colony)
2. Digestive cavity is saclike (only a mouth)
3. Outer epidermis, inner gastrodermis, and jellylike mesoglea between
4. Nerve net that coordinates sensory and motor activities
3. Reproduce asexually, and sexually (with swimming ciliated larva)
4. Flatworms, roundworms, rotifers – simple organ systems
1. Flatworms – 15,000 species (Table 28.2)
1. Body plan
1) Saclike gut (but none in tapeworms)
2) Bilateral symmetry, and cephalization
3) No coelom
4) Hermaphroditic – both sexes in one body
2. Planarians
1) Free-living, freshwater aquatic
2) Possess a pharynx tube that extends to feed
3) Flame cells – regulate body fluid volume
4) Asexual reproduction by fission of body
3. Flukes
1) Internal parasites of liver, lung, or blood
2) Complex life cycle – requires primary host for sexual reproduction, and intermediate host (usually a
snail)
4. Tapeworms (Fig. 20.14)
1) Internal parasites of vertebrate intestines
2) Body – scolex (head) and proglottids (segments)
2. Roundworms – 20,000 species
1. Most small and free-living, but some parasitic (ex., hookworms in human organs)
2. Bilateral symmetry, complete digestive tract in a pseudocoelom, cuticle covers and protects body
3. Rotifers – 1,800 species
1. Microscopic, multicelled aquatic animals
2. Complex, with a complete set of organs
E. Mollusks – 110,000 species
1. Body usually incl. head, foot, shell, mantle, gills, and radula
2. Gastropods – snails and slugs <also, conchs, periwinkles, sea hare, etc.>
a. "Belly footed" animals – most organs in spiraled shell
b. Torsion – 180 turn that places some organs toward the head
3. Bivalves – clams, scallops, oysters, mussels, etc.
a. Two shells for protection – formed by mantle <which also produces pearls>
b. No head; foot usually specialized for burrowing
c. Water and suspended food particles are drawn in by action of cilia on the gills
4. Cephalopods – squids, cuttlefishes, octopuses, nautiluses
a. Largest of the invertebrates
b. Body modified for active predatory life-style – tentacles, beaklike jaws, and jet propulsion
c. Closed circulatory system, nervous system well developed, eyes form images, learning and memory
possible
F. Annelids – segmented worms (15,000 species)
1. Annelid groups
a. Earthworms – valuable tillers of soil
b. Leeches – aquatic "blood suckers"
c. Polychaetes – marine worms (with tentacles and "gills")
2. Annelid adaptations [of the earthworm]
a. Extensive segmentation with internal partitions; fluid filled to provide a hydrostatic skeleton
b. Paired nephridia in every segment for body fluid and liquid waste control
c. Digestive system is complete; circulation is closed
G. Arthropods – 1,000,000+ species
1. Adaptations
a. Hardened exoskeleton of protein and chitin (plus calcium in some)
1) Flexible and lightweight; good barrier to water loss
b.
c.
d.
e.
f.
2) But, must be shed periodically
Fewer body segments – grouped to form head, thorax, and abdomen <or cephalothorax and abdomen>
Jointed appendages for feeding, sensing, and locomotion
"Breathe" using tubes (trachaeas) connected to holes (spiracles) in the abdomen segments
Multi-faceted compound eyes allow for wide angle of vision and motion perception, but not focusing
Metamorphosis – larval stages concentrate on feeding and growth; adults specialize in dispersal and
reproduction
1) Complete metamorphosis – egg, larva, pupa, adult
2) Incomplete metamorphosis – egg, "nymph," adult
3) Gradual metamorphosis – egg –> adult
4. Spiders and relatives – 25,000 species
1. Chelicerates <inclu. arachnids> – spiders, scorpions, ticks, mites, horseshoe crabs, sea spiders (Fig. 20.22)
1) Spiders – eight-legged predators that trap insects in webs
2) Mites – some free-living, others are pests of plants and animals
3) Ticks – blood-suckers and disease carriers
2. Body plan – chelicerae (piercing), pedipalps (grasping), open circulatory system, book lungs
5. Crustaceans – 35,000 species
1. Shrimps [and krills], lobsters, crayfishes, crabs, barnacles, copepods, pillbugs
2. Important components of food webs and some serve as human food
3. Body plan
1) Cephalothorax and abdomen; gills in aquatic ones; ventral nerve cord (Fig. 20.24)
2) Appendages – two pairs of antennae, a pair of mandibles and maxillae, and five pairs of legs
6. Millipedes and centipedes – long, segmented body with many legs
1. Millipedes
1) Cylindrical body with two pairs of legs on each body segment
2) Slow-moving vegetarians
2. Centipedes
1) Flattened body with one pair of legs on each body segment
2) Fast-moving carnivore of small invertebrates
7. Insects – 900,000+ species
1. Body plan
1) Three regions – head (sensory and feeding), thorax (locomotion – six legs, two pairs of wings), and
abdomen
2) Malpighian tubules process metabolic waste and aid in water retention
2. Most successful of all groups
8. Echinoderms – spiny skinned animals (6,000 species) (Fig. 20.30)
1. Sea stars (starfish), brittle stars, sea urchins, sand dollars, sea cucumbers, sea lilies, feather stars
2. Larvae are bilateral; adults are radially symmetrical
1) Five-rayed body plan; spines and skin gills
2) Tube feet (locomotion and capture of prey) connected to water vascular system
3) Sea stars feed on bivalve mollusks – can evert stomach for exterior digestion
Animals: The Vertebrates (chap 21)
1. Characteristics of chordates
1. Consists of mostly vertebrates, with a few invertebrate chordates
2. Four distinctive features, at some time in their lives
1. Notochord – long rod that supports the body; changes to bone in vertebrates
2. Dorsal, hollow nerve cord
3. Muscular pharynx with gill slits
4. Post-anal tail
3. Classified in three subphyla and eight classes (one of which is extinct)
2. Invertebrate chordates (Fig. 21.3)
1. Tunicates (sea squirts) – 2,000 species
1. Marine organisms covered with a gelatinous tunic
2. Larva resembles a tadpole
3. Adult is sessile and a filter feeder – only gill pouches persist
2. Lancelets – 25 species
1. Small fishlike animals
2. Lie buried in sand and filter feed
3. Display all four chordate characteristics throughout their lives
3. Jawless fishes
1. Earliest were the ostracoderms
1. Covered with hardened external plates
2. Lived on the ocean bottom and were filter feeders
2. Existing jawless fishes – lampreys and hagfishes (Fig. 21.7)
1. Have eel-like bodies (but no paired fins) with a cartilaginous skeleton, and two-chambered heart
2. Lampreys are parasitic on other fish; hagfishes are scavengers
4. Jawed fishes
1. Earliest were the placoderms – now extinct
2. Cartilaginous fishes – 850 species (Fig. 21.8)
1. Have a streamlined body with a cartilaginous skeleton, gill slits, paired fins, and two-chambered heart
2. Includes sharks, skates, rays, and chimaeras
1) Sharks are predators with powerful jaws and replaceable teeth (but, some are filter feeders)
2) Skates and rays live on the ocean bottom and feed on invertebrates – some are electric or can sting
3) Chimaeras resemble a rat
3. Bony fishes – 20,000 species (Figs. 21.9 & 21.10)
1. Most numerous and diverse of the vertebrates
2. Have a streamlined body (exclu. sea horse) with a bony skeleton, gill flaps, paired fins, two-chambered
heart, and swim bladder; most have scales
3. Lobe-finned fishes bear fleshy extensions – coelacanth and lung fishes
4. Ray-finned fishes – modern fish
5. Amphibians (Fig. 21.12)
1. Evolved from lobed-finned fishes
2. Land life represented new challenges
1. Water availability was not reliable
2. Air temperature was variable; air was not the supporting medium that water was, but was a richer source of
oxygen
3. New habitats made better sense organs necessary; lots of insects for food
3. General characteristics
1. Bony skeletons, usually four legs, and a three-chambered heart
2. Respiration by gills, or by lungs and moist skin (skin supplied with poisonous glands in toads)
3. Most shed their eggs into water, and have a “tadpole” larva
4. Includes salamanders (have tails), frogs and toads – 3,000+ species, and caecilians (“worm-like”) – 150
species
6. Reptiles (Fig. 21.13)
1. Evolved from amphibians
2. General characteristics
1. Bony skeletons, four legs, and a three-chambered heart (four-chambered in crocodilians, and possibly
dinosaurs)
2. Scaly skin that resists drying; kidneys are good at conserving water
3. Have a copulatory organ that permits internal fertilization; produce shelled eggs which can be laid in dry
habitats
3. Includes crocodilians, turtles, tuataras, and lizards and snakes
1. Crocodilians – crocodiles and alligators
1) Live in or near water; parents guard nests and assist hatchlings into water
2) Long snouts; body temperature is regulated behaviorally (“sunning”)
2. Turtles – shell for protection (150 species)
3. Tuataras – resemble lizards, but more ancient; only two species, on islands near New Zealand
4. Lizards and snakes
1) Lizards – small bodied insect eaters; live mostly in deserts or tropical forests (3,750 species)
2) Snakes – limbless; excellent predators (poisonous or non-poisonous) (2,300 species)
7. Birds – 9,000 species (Figs. 21.14 & 21.15)
1. Evolved from small dinosaurs during the Jurassic
1. Oldest known bird – Archaeopteryx
2. Reptilian features of birds – horny beaks, scaly legs, and egg-laying
2. General characteristics
1. Body covered with feathers (contour feathers for flight, down feathers for insulation)
2. Constructed for flight – low weight and high power
1) Hollow lightweight bones; powerful muscles for maximum leverage
2) Four-chambered heart and unique lung design
8. Mammals – 4,500 species (Fig. 21.17)
1. Evolved from small dinosaurs during the Carboniferous
2. General characteristics
1. Hair covers at least part of the body (except in whales); milk-secreting glands nourish the young
2. Increased brain capacity, allowing for memory, learning, and conscious tought
3. Teeth (incisors, canines, premolars, and molars) specialized to meet dietary habits
3. Reproduction
1. Egg-laying mammals
1) Platypus and spiny anteater (Australia)
2) Modified sweat glands for milk
2. Pouched mammals – marsupials
1) The young are born tiny, blind, and hairless; finish their development in mother’s pouch
2) Most are in Australia, but opossum thrives in North America
3. Placental mammals
1) The young are nourished within mother’s uterus by the placenta
2) Major orders <Not in textbook.>
1) Bats – 925 species
2) Rodents – 1,760 species (mice, rats, squirrels, beavers, porcupines)
3) Hoofed mammals – 200+ species (horses, goats, zebras, elks, deer, etc.)
4) Rabbits, hairs, pikas – 65 species
5) Carnivores – 270 species (dogs, cats, bears, raccoons, skunks, etc.)
6) Elephants – 2 species
7) Whales, dolphins (porpoises) – 80 species
8) Primates – 180 species (lemurs, monkeys, chimpanzees, gorillas, humans)
9. Evolutionary trends among the primates
1. Primate classification
1. Prosimians – oldest line (ex., lemurs)
2. Tarsioids – Southeast Asia
3. Anthropoids – monkeys, apes, and humans
1) Hominoids – apes and humans
2) Hominid – humans
2. Key evolutionary trends
1. Most primates live in tropical or subtropical regions
2. Five trends that define primate lineage
1) Enhanced daytime vision (inclu. color vision)
2) Upright walking
3) Precision grip and power grip
4) Teeth for all occasions
5) Better brains, bodacious behavior
3. From primates to hominids
1. Primates evolved about 60 million years ago (first resembled rodents or tree shrews; then developed larger
brains and became the ancestors of monkeys and apes)
2. Hominoids appeared about 20 million years ago
1) Ranged over forests and grasslands of the Old World
2) Branched into three lines – gorillas, chimps, and humans
3. The first hominids – australopiths (Fig. 21.23)
1) Most of the earliest hominids lived in the East African Rift Valley
2) General characteristics
1) Were upright walkers, with hands freed for new tasks
2) Modifications in teeth and jaws allowed for a more varied diet
3) More elaborate brain permitted thinking and reasoning
4. Emergence of humans
1) Hominids began to use stone tools about 2.5 million years ago – Homo habilis
2) Homo erectus made advanced tools and used fire
3) Homo sapiens evolved from H. erectus between 300,000 and 200,000 years ago
4) Neanderthals were similar to modern humans but disappeared 35,000-40,000 years ago
Population Ecology (chap 35)
A. Ecology -- study of interactions of organisms with one another and with their environment
B. Characteristics of populations
1. Population -- group of individuals of the same species living in the same area (habitat)
a. Population size -- number of individuals making up its gene pool
b. Population density -- number of individuals per unit area (or volume)
c. Population distribution -- general pattern in which population members are dispersed through their habitat
d. Age structure -- relative proportions of individuals of each age (esp. with respect to reproductive years)
2. Population dispersal patterns
a. Clumped -- very common
b. Uniform -- rare, usually the result of fierce competition for limited resources
c. Random -- environmental conditions are uniform and members are neither attracting nor repelling each
other
C. Population size and exponential growth
1. How population size changes
a. Population size dependent on births, immigration, deaths, and emigration
b. Population size increases if there are more births than deaths, and decreases if there are more deaths than
births
c. Zero population growth -- balance of births and deaths
2. Growth patterns are exponential
a. Growth rate formula -- G = rN
1) r -- net reproduction per individual per unit time
2) N -- number of individuals
b. Results in a J-shaped curve that becomes steeper with time (Fig. 35.2)
c. As long as "r" is positive, population will continue to increase at ever-increasing rates
d. Doubling time -- amount of time to double the population
3. Biotic potential -- maximum rate of increase under ideal (nonlimiting) conditions
D. Limits on growth of populations
1. Limiting factors
a. Actual rate of increase of a population is influenced by environmental conditions
b. Limiting factors (nutrient supply, predation, competition for space, pollution, metabolic wastes) provide
environmental resistance to population growth
2. Carrying capacity and logistic growth
a. Carrying capacity -- defined by the sustainable supply of resources for a particular population in a given
environment
b. Logistic growth -- S-shaped curve caused by the carrying capacity varying over time
3. Density-dependent controls
a. Main density-dependent factors -- competition for resources, predation, parasitism, disease, etc.
b. These factors exert their effects in proportion to the number of individuals present
4. Density-independent controls
a. Tend to increase the death rate without respect to the number of individuals present
b. Ex. -- weather (lightning, floods, snowstorms, etc.)
E. Life history patterns
1. Life tables -- follow the fate of a groups of newborn individuals (cohort) through their lives to calculate
survivorship schedules
2. Survivorship curves -- plots of age-specific patterns of death for a given population in a given environment
(Fig. 35.5)
a. Type I curve -- typical of large mammals, where infant mortality is low; death usually comes after an
extended life
b. Type II curve -- chances of survival or death are about the same at any age
c. Type III curve -- low survivorship or high mortality in early life
F. Human population growth (Fig. 35.7)
1. Statistics
a. World population reached 5.7 billion in 1995
b. Each year about 90 million more people are born (about 10,700 per hour)
2. How we began sidestepping controls
a. Humans expanded into new habitats and new climatic zones
b. Agriculture increased the carrying capacity of the land
c. Medical practice and improved sanitation removed many population-limiting factors
3. Present and future growth
a. It took 2 million years for human population to reach 1 billion; it took only 12 years to go from 4 to 5
billion
b. Even at a growth rate of 1.6%, human population is rapidly reaching a size that is not sustainable
G. Control through family planning (Fig. 35.8)
1. At present rate of increase, world human population will be 8.5 billion in 30 years
a. Even if replacement level of fertility is achieved (2 children per woman), human population will continue
to grow for another 60 years
b. Effective family planning programs can achieve a faster decline in birth rate than economic development
alone
2. Total fertility rate -- average number of children born to women during their reproductive years (Fig. 35.9)
a. Population with broadly based age structure (many women in reproductive years) will continue explosive
population growth
b. One way to slow birth rate is to bear children in early 30's, rather than mid-teens or 20's
H. Population growth and economic development
1. Demographic transition model -- changes in population growth are linked to four stages of economic
development (Fig. 35.11)
a. Preindustrial stage -- living conditions harsh, birth and death rates are high; little increase in population
size
b. Transitional stage -- living conditions improve, death rate drops, birth rate remains high
c. Industrial stage -- growth slows
d. Post- industrial stage -- zero population growth is reached; birth rate falls below death rate
2. Developed countries are in industrial stage (ex., U.S., Canada, Japan); some countries (ex., Mexico) are in
transitional stage
3. U.S. may not be overpopulated in terms of numbers (as, say India), but it may be in terms of resource
consumption (U.S. has 4.7% of world's population, but uses 21% of all goods and services)
I. Social impact of no growth
1. How can aging population be supported by a decreasing younger population?
2. Can humans defy laws of nature that dictate the number of individuals which can be supported per unit of
space?
Community Interactions (chap 36)
1. Factors that shape community structure
1. Community – association of interacting populations of different species living in a particular habitat
1. Habitat – place where an organism lives; characterized by distinctive physical features and vegetation
1) Interactions between climate and topography dictate rainfall, temperature, soil composition, etc.
2) Availability of food and resources affects inhabitants
3) Adaptive traits enable individuals to exploit specific resources
4) Interactions of various kinds (competition, predation, mutualism) occur among the inhabitants
5) Physical disturbances, immigration, and episodes of extinction affect the habitat
2. Several community properties result from factors above
1) Species are found at different feeding levels from producers to consumers
2) Diversity increases in tropical climates, creating species richness
2. Niche – the “occupation” of a species
1. Defined by the full range of physical and biological conditions under which the individual lives and
reproduces
2. Each species has its own niche defined, in part, by its relationships with other organisms
3. Categories of species interactions
1. Interactions can occur between any two species in a community and between entire communities
2. Several types of species interactions
1) Neutral – neither species directly affects the other (ex., eagles and grass)
2) Commensalism – one species benefits and the other is not affected (ex., bird’s nest in tree)
3) Mutualism – both species benefit (ex., lichens, yucca plant and yucca moth)
4) Interspecific competition – both species are harmed
5) Predation and parasitism – one species benefits while the other is harmed
2. Competitive interactions
1. Categories of competition
1. Intraspecific – competition within a population of the same species; may result in depletion of a resource
2. Interspecific – competition between species; less intense because requirements are less similar
3. Two types, regardless of whether they are intra- or interspecific
1) Exploitation competition – all individuals have equal access to a resource, but differ in their ability
(speed or efficiency) to exploit that resource
2) Interference competition – some individuals limit others’ access to the resource
2. Competitive exclusion – two species require the same resource
1. Suggests that complete competitors cannot coexist indefinitely; differences in adaptive traits give certain
species the competitive advantage
2. When competitors’ niches do not overlap as much, coexistence is more probable
3. Resource partitioning
1. Similar species share the same resources in different ways
2. Resource partitioning arises in two ways
1) Ecological differences between established and competing populations may increase through natural
selection
2) Only species that are dissimilar from established ones can succeed in joining an existing community
3. Predation and parasitism
1. Predator vs. parasite
1. Predators – get their food from prey, but do not take up residence on or in the prey
2. Parasites – get their food from hosts, and live on or in the host for a good part of their life cycle
2. Dynamics of predator-prey interactions
1. The dynamics, ranging from stable coexistence to recurring cycles, depend on:
1) Carrying capacity of prey population in the absence of predation
2) Reproductive rates of prey and predator
3) Behavioral capacity of individual predators to respond to prey density
2. Stable coexistence results when predators prevent prey from overshooting the carrying capacity
3. Fluctuations in population density tend to occur when predators do not reproduce as fast as their prey,
when they can eat only so many prey, and when carrying capacity for prey is high
3. Parasite-host interactions
1. True parasites live in or on a host and gain nourishment by tapping into its tissues (ex., flukes and
tapeworms)
2. Parasites and hosts tend to survive together; parasites do not usually kill their hosts
4. Parasites as biological control agents
1. Have five attributes that make them good control agents
1) Well adapted to the host species and their habitat
2) Are exceptionally good at searching for hosts
3) Growth rate is high relative to that of the host species
4) Are mobile enough for adequate dispersal
5) Lag time between responses to changes in numbers of host population is minimal
2. Care must be taken in releasing more than one kind of control agent in a given area due to the possibility of
triggering competition among them and lessening their overall level of effectiveness
5. Coevolutionary arms race
1. Camouflage – have adaptations that permit blending with surroundings and escape detection
2. Warning coloration (ex., monarch butterfly) – have conspicuous patterns that serve as warning signals to
predators
3. Mimicry (ex., viceroy butterfly) – closely resemble unpalatable or dangerous species
4. Moment-of-truth defenses – ex., warning odors, repellants, poisons
5. Adaptive responses to prey – predators counter prey defenses with their own adaptations
4. Succession
1. Successional model
1. Succession – predictable development of species in a community
1) Pioneer species are first to colonize an area, followed by more competitive species
2) Climax community – persistent array of species that results after some lapse of time
2. Primary succession – happens in an area that was devoid of life (ex., bare rock, open water, etc.)
3. Secondary succession – community reestablishes itself to a climax state after a disturbance (ex., forest fire,
abandoned field, etc.)
2. Climax-pattern model – community is adapted to total pattern of environmental factors (climate, soil,
topography, wind, fires, etc.) to create a continuum of climax stages of succession
3. Cyclic, nondirectional changes
1. Community stability may require episodes of instability that permit replacement of equilibrium species
2. Ex. – fires in forests of California that rid the area of underbrush
5. Community instability
1. Over the short-term, disturbances can hamper growth of some species, and long-term changes in climate may
have destabilizing effects
2. How keystone species tip the balance
1. Keystone species – dominant that dictates community structure
2. Ex. – tall trees in forest; starfish control the abundance of bivalves
3. How introduced species tip the balance
1. A population may expand its home range by gradually diffusing into hospitable outlying regions
2. Individuals may be rapidly transported across great distances
1) Some introduces species are beneficial – ex., soybeans, rice, wheat, corn, potatoes, etc.
2) Others are “bad” – water hyacinth, kudzu, hares in Australia, gypsy moths, zebra mussels, killer bees,
etc.
3. A population may move from its home range over geologic time, by continental drift
6. Patterns of biodiversity
1. Mainland and marine patterns
1. Number of species increases from Arctic regions to temperate zone to tropics
2. Diversity is favored in the tropics for three reasons
1) More rainfall and sunlight provides more food reserves
2) Rate of speciation has exceeded the rate of extinction
2. Island patterns
1. Islands distant from source areas receive fewer colonizing species (ex., Galapagos islands, Hawaiian
islands)
2. Larger islands tend to support more species (ex., Australia)
Ecosystems (chap 37)
1. The nature of ecosystems
1. Ecosystem – a complex of organisms interacting with each other and with the physical environment
1. Are open systems through which energy flows and materials are cycled
2. Require energy and nutrient input and generate energy (usually as heat) and nutrient output
2. The participants
1. Producers – autotrophs that can capture sunlight energy and incorporate it into organic compounds
2. Consumers – heterotrophs that feed on tissues of other organisms
1) Herbivores – eat plants
2) Carnivores – eat animals
3) Omnivores – eat a variety of organisms
4) Parasites – reside in or on living hosts and extract energy from them
3. Decomposers – heterotrophs (inclu. bacteria and fungi) that extract energy from the remains or products of
organisms
4. Detritivores – small invertebrates that feed on partly decomposed particles of organic matter (detritus)
3. Structure of ecosystems
1. Trophic (feeding) levels
1) Level 1 – producers
2) Level 2 – herbivores
3) Level 3 – carnivores
4) Decomposers feed on organisms from all levels
2. Food webs
1) Food chain – sequence of what eats what
2) Food web – interconnected food chains in which the same food resource is often part of more than one
food chain
2. Energy flow through ecosystems
1. Primary productivity
1. Def. – The rate of photosynthesis for the ecosystem during a specified interval of time
2. Net primary productivity – the rate of energy storage in plant tissues in excess of the rate of respiration by
the plants themselves
2. Major pathways of energy flow
1. Energy flows into ecosystem from the sun
1) Grazing food webs – energy flows from plants to herbivores and then to carnivores
2) Detrital food webs – energy flows from plants through decomposers and detritivores
2. Energy leaves ecosystems through heat losses generated by metabolism
3. Ecological pyramids
1. Trophic (feeding) structure can be diagrammed as a pyramid in which producers form the base for
successive tiers of consumers above them
2. Two basic types of pyramids
1) Pyramid of biomass – uses the weight of the members in each trophic level
2) Pyramid of energy – based on energy losses at each level
3. Biogeochemical cycles
1. Overview
1. Biogeochemical cycles influence the availability of essential elements in ecosystems
1) Elements are available to producers as ions
2) The amount of nutrients being recycled <through living organisms> is greater than the amount entering
or leaving <from other sources>
2. Three categories of biogeochemical cycles
1) Hydrologic cycle – oxygen and hydrogen move as water molecules
2) Atmospheric cycles – elements move in the gaseous phase (ex., carbon & nitrogen)
3) Sedimentary cycles – element does not have a gaseous phase (ex., phosphorus)
2. Hydrologic cycle
1. Water is moved or stored by evaporation, precipitation, retention, and transportation
2. Water moves other nutrients in or out of ecosystems
1) Watershed – funnels rain or snow into a single river
2) Nutrients are absorbed by plants and prevent their loss by leaching
3. Carbon cycle
1. Carbon enters the atmosphere (as carbon dioxide) by aerobic respiration, fossil-fuel burning, and volcanic
eruptions
2. Carbon is removed from the atmosphere (and bodies of water) by photosynthesis and by shelled organisms
3. Decomposition of buried carbon compounds millions of years ago caused the formation of fossil fuels (ex.,
coal, oil, natural gas)
4. Burning of fossil fuels puts extra amounts of carbon dioxide into the atmosphere, and may lead to global
warming (the greenhouse effect)
4. Nitrogen cycle
1. Nitrogen – needed for production of proteins and nucleic acids (DNA & RNA)
1) Abundant in the atmosphere (80%), but not in the earth’s crust
2) Of all nutrients needed for plant growth, nitrogen is the scarcest
2. Complicated cycle <as compared to the others>
1) Nitrogen fixation – bacteria convert nitrogen gas to a form that plant roots can use directly
2) Decomposition and ammonification – caused by bacteria and fungi feeding on dead plants and animals
(or animal waste products)
3) Nitrification – ammonia (or ammonia compound) is converted into a nitrite and then into a nitrate
4) Denitrification – release of nitrogen gas to the atmosphere by the action of bacteria on nitrites and
nitrates
3. Humans affect the cycling of nitrogen compounds
1) Air pollutants (incl. oxides of nitrogen) contribute to soil acidity <acid rain>
2) Heavy nitrogen fertilizer applications are costly and are lost in runoff and harvested crops
5. Phosphorus cycle
1. Long-term geochemical phase – phosphorus moves from land, to sediments in the seas, and back to the
land
2. Ecosystem phase – plants take up phosphorus from the soil, transfers it to herbivores and then to
carnivores, which excrete it in waste products and decomposing bodies
4. Predicting the impact of change in ecosytems
1. Ecosystem modeling
1. Tries to predict the complex effects of a single change in an ecosystem
2. Computer modeling is valid, if all of the key relationships in the ecosystem have been incorporated into the
model
2. Biological magnification – DDT
1. An effective chemical in killing mosquitoes, but accumulated in fatty tissues and causes unexpected
nontarget effects <ex., brittle egg shells>
2. DDT now banned in the U.S., and some of the effects have begun to reverse
The Biosphere (chap 38)
A. Biosphere – earth regions where organisms live
1. Definitions
a. Hydrosphere – all water on or near the earth's surface
b. Lithosphere – earth's outer, rocky layer
c. Atmosphere – gases, particles, and water vapor enveloping the earth
2. Global patterns of climate
a. Climate – includes temperature, humidity, wind velocity, cloud cover, and rainfall
b. Shaped by four factors
1) Variations in the amount of incoming radiation
2) Earth's daily rotation and annual revolution
3) World distribution of continents and oceans
4) Elevation of land masses
B. Air circulation patterns and regional climates (Fig. 38.5)
1. Atmosphere has mediating effects on the earth's climate
a. Ultraviolet radiation is absorbed by ozone and oxygen in the upper atmosphere
b. Clouds, dust, and water vapor absorb and reflect solar radiation
c. Radiation warms the earth's surface, generating heat that drives the weather systems
2. Heating from the sun results in air currents <winds>
a. Sun differentially heats equatorial and polar regions, creating the world's temperature zones
b. Warm equatorial air rises, cools, releases it moisture, and spreads N and S where it descends at 30
latitudes as very dry air (results in deserts)
c. The air is warmed again and ascends at 60 latitudes
d. Amount of solar radiation reaching the earth's surface changes in the N and S hemispheres <due to the
earth's tilt>
C. The ocean, land forms, and regional climates
1. Ocean currents and their effects
a. Ocean water covers 71% of the earth's surface
b. Latitude and seasonal variations in solar heating cause warming and cooling
c. Surface waters move from the equator to the poles, warming the air above
d. Immense circular water movements form in the Atlantic and Pacific oceans
2. Rain shadows and monsoons
a. Topography – physical features of a region (ex., elevation)
b. Mountains and valleys influence regional climates
1) Monsoon rains – occur when warm winds pick up ocean moisture and release it over the cooler land
masses of Asia and Africa
2) Mountains of the W U.S. cause the winds from the ocean to rise, cool, and lose their moisture <causing
a rain shadow effect on the leeward (eastern) slopes
D. The world's biomes
1. Definitions
a. Biogeography – the study of the global distribution of species
b. Biogeographic realms (6 of them) – broad land regions with characteristic types of plants and animals
c. Biomes – broad vegetational subdivisions (including all animals and other organisms)
2. Soils of major biomes
a. Soil – mixture of rock, mineral ions, and organic matter
1) Size of the mineral component can range from gravel, to sand, silt, and clay
2) The organic matter is called humus
b. Soil profiles – defined by the composition of soil from the surface downward
1) Topsoil has the most humus, but is vulnerable to weathering
2) Loam topsoils have the best mix of sand, silt, and clay for agriculture
3. Deserts
a. Areas where evaporation exceeds rainfall [30 N and S latitudes]
1) Vegetation is scarce
2) Day/night temperatures fluctuate widely
b. More than 1/3 of the world's land area is arid (or semiarid) due to drought and overgrazing, which can lead
to desert formation
4. Dry shrublands, dry woodlands, and grasslands
a. Dry shrublands and dry woodlands – W or S coastal regions of continents between 30 and 40 N and S
latitudes
1) Climate is semiarid (rains occur during mild winter months); summers are long, hot, and dry
2) Dry shrublands – rainfall is less than 25-60 cm (ex., California chaparral)
3) Dry woodlands – rainfall 40-100 cm; there are trees but not dense forests
b. Grasslands – extend across the interior of continents between deserts and temperate forests
1) Characteristics – flat or rolling land, high rates of evaporation, limited rainfall, grazing and burrowing
animals
2) Several types
a) Shortgrass prairie, tallgrass prairie (U.S. mW and W)
b) Savannas (ex., Africa), monsoon grasslands (S Asia)
5. Tropical rainforests and other broadleaf forests
a. Evergreen broadleaf forests (ex., tropical rain forest) – between 20 N and S latitude
1) Temperatures, rainfall, and humidity are all high
2) Plant growth is luxuriant, with incredible animal diversity
b. Deciduous broadleaf forests – common at temperate latitudes
1) Tropical deciduous forest, monsoon forests (of SE Asia)
2) Temperate deciduous forests (of North America)
6. Coniferous forests
a. Typical tree is some variety of evergreen cone-bearer with needlelike leaves
b. Found in widely divergent geographic areas
1) Boreal forests (taiga) – found in cool to cold N regions of North America, Europe, & Asia (spruce &
balsam fir)
2) Montane coniferous forests – extend S through the great mountain ranges (fir & pine)
3) Temperate rain forest – W coast of North America (sequoias & redwoods)
4) Pine barrens – in sandy soil of several E coast states
7. Tundra
a. Arctic tundra
1) A vast treeless plain N of the boreal forests
2) Very cold, with low moisture; characterized by permafrost
b. Alpine tundra – occurs at high elevations in mountain throughout the world
E. Aquatic provinces
1. Freshwater provinces
a. Lake ecosystems
1) Body of freshwater with three zones
a) Littoral zone – extends from the shore to where rooted plants stop growing
b) Limnetic zone – open, sunlit waters beyond the littoral zone to a depth where photosynthesis is no
longer significant; plankton life is abundant
c) Profundal zone – deep, open water below the depth of light penetration
2) In temperate regions, lakes undergo <seasonal> changes in density and temperature
a) Winter – ice (less dense) forms on the surface over water that is warmer (4C) and denser
b) Spring overturn – warming and winds cause oxygen to be carried downward and nutrients to the
surface
c) Midsummer – a thermocline between the upper warmer layers and lower cooler layers prevents
vertical warming
d) Fall overturn – upper layers cool and sink
3) Lakes and nutrients
a) Oligotrophic lakes – deep, nutrient-poor, and low in primary productivity
b) Eutrophic lakes – shallow and nutrient-rich (often due to agricultural and urban runoff wastes)
b. Stream ecosystems
1) Start out as freshwater springs or seeps
2) Three kinds of habitats from head waters to river's end
a) Riffles – shallow, turbulent stretches
b) Runs – fast-flowing waters with a smooth surface
c) Pools – slow-moving deep waters
2. Ocean provinces
a. The ocean consists of two vast provinces
1) Benthic province – includes all of the ocean bottoms
2) Pelagic province – includes the entire volume of ocean water
a) Neritic zone – the relatively shallow water overlying the continental shelves
b) Oceanic zone – the water over the ocean basins; photosynthesis is restricted to the surface
b. Primary productivity
1) Phytoplankton are at the bottom of food chains; organic remains and wastes enter the detrital webs
2) About 70% of the productivity comes from microscopic phytoplankton
c. Hydrothermal vents
1) In fissures between the earth's plates; water becomes heated and laden with minerals
2) Elaborate food webs based on mineral-feeding bacteria
3. Coral reefs and banks
a. Coral reefs are the accumulated remains of countless corals, etc.
1) Most are located in clear, warm sea waters of the tropics
2) Human activities are destroying the reefs with pollution and physical damage
b. Coral banks are located farther N and S at the edges of the continental shelves near Japan, California,
Norway, England, and New Zealand
4. Life along the coasts
a. Estuaries
1) Partially enclosed regions where fresh and salt water meet
2) Incredibly productive feeding and breeding grounds
b. Intertidal zone
1) Alternately exposed and submerged; existence is difficult
2) Rocky shores – have three vertically arranged zones
a) Upper littoral – submerged only during the highest tides; it is sparsely populated
b) Mid-littoral – submerged during the regular high tide and exposed at low tide
c) Lower littoral – exposed only during the lowest tides
3) Sandy and muddy shores
a) Unstable stretches of loose sediments
b) Detrital food webs occur; invertebrates are plentiful
c. Upwelling along coasts
1) Upwelling – upward movement of deep, nutrient-rich water along margins of continents
a) Under the influence of N winds and the earth's rotation, water along the W coast of the N
Hemisphere moves W where cold, deep water moves in vertically to replace it
b) Nutrients circulate and primary productivity increases
2) Ever 3-7 years, the warm surface waters of the W equatorial Pacific move E to the coasts of C & S
America, causing a downwelling (El Nino)
Human Impact on the Biosphere (chap 39)
A. Human indifference – population growth and individual demands are stressing the environment (Fig. 39.1)
B. Air pollution
1. Pollutants – substances with which ecosystems have no prior experience and therefore cannot deal with them
a. Include carbon dioxide, oxides of nitrogen and sulfur, and chlorofluorocarbons
b. Each day 700,000 metric tons of pollutants are dumped into the atmosphere in the U.S.
2. Smog – thermal inversions can trap pollutants close to the ground (Fig. 39.2)
a. Industrial smog – gray air found in industrial cities that burn fossil fuels
b. Photochemical smog – brown air (ex., auto exhaust) found in large cities in warm climates
3. Acid deposition
a. Burning coal produces sulfur dioxides; fertilizers and burning fossil fuels produce nitrogen oxides
b. Tiny particles of these oxides fall to Earth as dry acid deposition or acid rain (Fig. 39.3)
4. Ozone holes (Fig. 39.5)
a. Ozone in the lower stratosphere absorbs most of the ultraviolet radiation from the sun
1) Thinning of the ozone layer has produced an ozone hole over Antarctica
2) In response, skin cancer has increased, cataracts may increase, and phytoplankton may be affected
b. Chlorofluorocarbons (CFCs) seem to be the cause
1) One chlorine atom can convert 10,000 ozone molecules to oxygen
2) Other ozone "eaters" include methyl bromide, jet vapor trails, and methane
C. Solid wastes, and food production
1. Solid waste disposal
a. Paper products and nonreturnable bottles and cans are our biggest problems
b. Need to move from a "throwaway" society to one of conservation and reuse
2. Converting marginal lands to agriculture
a. 21% of land is used for agriculture; another 28% is available but may not be worth the cost
b. The "Green Revolution" has increased crop yields, but uses many times more energy and mineral resources
c. Growing human population is moving into marginal lands to meet its increasing needs
3. Deforestation (Fig. 39.7)
a. Forests are watersheds that control erosion, flooding, and sediment buildup in rivers and lakes
1) Deforestation can reduce fertility, change rainfall patterns, increase temperatures, and increase carbon
dioxide
2) Clearing large tracts of tropical forests may have global repercussions (inclu. alteration of rates of
evaporation, transpiration, runoff, and rainfall as well as photosynthetic activity rates
b. In "slash-and-burn" agriculture, trees are cut, the land used for a few growing seasons, and then abandoned
as fertility plummets
4. Grasslands into deserts
a. Desertification – conversion of grasslands and croplands to desertlike conditions
1) The term also applies when agricultural productivity drops by 10% or more
2) At least 200,000 square kilometers are being converted annually
b. Large-scale desertification is caused by overgrazing of cattle on marginal lands
D. Global water crisis
1. Most of Earth's water is too salty for human consumption or for agriculture
2. Consequences of heavy irrigation
a. Large-scale agriculture accounts for nearly 2/3s of the human population's use of fresh water
b. Salt buildup (salination) of the soil and waterlogging can result
c. Withdrawal of underground water causes water tables to drop
3. Water pollution
a. Caused by human waste, insecticides, herbicides, chemicals, radioactive materials, and heat
b. Wastewater treatment
1) Primary treatment – removes and burns sludge before it is dumped in landfills; chlorine is added to
water
2) Secondary treatment – uses microbes to degrade organic matter; but nitrates, viruses, and toxic
substances remain
3) Tertiary treatment – uses experimental methods to remove solids, phosphates, organics, etc.; used on
about 5% of the nation's wastewater
c. The coming "Water Wars"
1) In the past decade, 33 nations have engaged in conflicts over reductions in water flow, pollution, and silt
buildup
2) By restricting water flow, countries upstream may attempt to influence political behavior in countries
downstream
E. Energy inputs
1. Increases in human population and extravagant life-styles increase consumption
2. Fossil fuels
a. Are a limited <non-renewable> resource – extraction costs are increasing, and atmospheric levels of carbon
dioxide and sulfur dioxides are also increasing
b. Extraction and use of abundant reserves of oil shale and coal are not "environmentally attractive"
3. Nuclear energy
a. The net energy produced is low and the cost high compared with coal-burning plants
b. Meltdowns may release large amounts of radioactivity to the environment
c. Nuclear waste is so radioactive that it must be isolated for 10,000 years
4. Alternative energy sources
a. Solar-hydrogen energy
1) An attractive technology because it depends on a "limitless" energy source -- the sun
2) Photovoltaic cells produce an electric current that splits water into oxygen and hydrogen gas which can
be used directly as fuel or to produce electricity
b. Wind energy
1) Where winds travel faster than 7.5 meters/second, wind turbines are cost-effective producers of
electricity
2) Because winds do not blow on a regular schedule, wind turbines cannot be the exclusive source of
energy
c. Fusion power
1) Temperature like those on the sun cause atomic nuclei to fuse and release energy
2) Fusion power is possible, but many obstacles make the technology a distant possibility